The substituted pyridines, especially, halo substituted trifluoromethylpyridines are key intermediates in the synthesis of pesticides, insecticides, herbicides and the like. It is also widely used in organic synthesis, pharmaceuticals and dye.
The U.S. Pat. No. 4,563,529 provides a process for producing trifluoromethylpyridine, by reacting a pyridine derivative selected from α-picoline, γ-picoline and a lutidine with chlorine and anhydrous hydrogen fluoride under inert gas atmosphere at a temperature of 300° C. to 600° C. in vapour phase in the presence of a diluent and a catalyst comprising a fluoride of a metallic element. The process produces 6-chloro-2-trifluoromethyl pyridine with a low yield ranging from 37.4% to 48.3% by gas chromatography.
The present inventors observed that prior art generates low yield of 2-chloro-6-trifluoromethylpyridine with low purity along with the formation of excess bi-products. The present invention provides a process for the preparation of substituted pyridines, especially, halo substituted trifluoromethylpyridines which is simple, easy to perform and industrially doable. The present invention provides halo substituted trifluoromethylpyridines with high yield. Additionally, the present invention has advantage of advanced catalyst life.